The present invention relates to the separation of phenols from phenol-containing streams and converting them to ethers by use of one or more multivalent metal oxides and/or hydroxides, whereupon the resulting hydroxy metal-phenate is reacted with a quaternary ammonium or phosphonium salt or base.
The presence of phenols in various hydrocarbonaceous streams is troublesome. For example, the presence of phenol functionality in liquids produced from coal causes instability of these liquids over a period of time by increasing the viscosity, the color intensity, and causing separation of resinous materials. Moreover, without extensive hydrotreatment, coal liquids are generally not compatible with petroleum liquids of comparable boiling point. Thus, solids separation caused largely by high concentrations of phenols leads to severe operability problems for coal/petroleum liquid blends. Also, hydrodesulfurization and hydrodenitrogenation of coal liquids are required prior to reforming into gasoline. These steps generally require substantial consumption of hydrogen for phenol-rich coal liquids because of the extensive deoxygenation of phenols to water.
Various methods of separating these troublesome phenols from hydrocarbonaceous streams are taught in the art. For example, it is taught that weakly acidic organic substances such as phenols can be removed from hydrocarbonaceous streams by use of alkali metal or alkaline-earth metal oxides or hydroxides. It is also taught that the phenols react with these oxides or hydroxides resulting in this formation of phenoxide salts which can be easily separated from the purified stream. Further, it is known that certain phenoxide salts, such as calcium phenoxide, can be heated in the presence of carbon dioxide to yield phenols and calcium carbonate.
Another method taught for separating phenols from hydrocarbonaceous streams is to wash the stream with large quantities of water or aqueous caustic solutions such as sodium or potassium hydroxide.
Although such methods are practiced on a commercial scale in various industries, there is still a need to develop a process for removing, from hydrocarbonaceous streams, troublesome phenols, recovering the phenols in a more efficient and inexpensive way and converting the phenols to more non-polar species which would be more compatible with petroleum liquids.